1. Field of the Invention
The present invention relates generally to a method of recording and reproducing a color video signal and to a digital video tape recorder. More particularly, this invention relates to a digital video tape recorder for recording and reproducing a color video signal which is compatible with a conventional digital video tape recorder with a format of 4:2:2 type while keeping a double recording capacity.
2. Description of the Prior Art
There is known a digital video tape recorder for recording and reproducing a digital color video signal in 4:2:2 formatted digital video signal processing. FIGS. 1A to 1C illustrate this digital video processing. As the digital video data D.sub.VDS a luminance signal Y is sampled at a sampling frequency of 13.5 MHz and two difference chrominance signals B-Y and R-Y are sampled at a sampling frequency of 6.75 MHz, which is half of that luminance signal. A digital signal D.sub.Y formed of the luminance signal is recorded in the signal band of 6 MHz (5.75 MHz in practice). The digital signals D.sub.B-Y and D.sub.R-Y formed of the two difference chrominance signals B-Y and R-Y are recorded in the signal band of 3 MHz (2.75 MHz in practice).
When the digital video tape recorder based on of 4:2:2 format digital video signal processing is used to produce a picture in a broadcasting station or in production, the digital signals D.sub.B-Y and
D.sub.R-Y formed of the two difference chrominance signals B-Y and R-Y are recorded in the signal band of 3 MHz, which is a half of that of the digital signal D.sub.Y formed of the luminance signal. When the picture is edited by using a chromakey method, a satisfactory efficiency can not be demonstrated.
Further, according to the format of 4:2:2 type digital video signal processing, only the luminance signal the digital signals D.sub.Y and D.sub.B-Y and D.sub.R-Y formed of the two difference chrominance signals are recorded on the magnetic tape. In practice a key signal or the like for achieving a special effect can not be recorded thereon. Therefore, in the production of pictures, the key signal is recorded by another video tape recorder using a complicated method causing complicated and cumbersome work.
In order to solve the above-mentioned problems, a so-called 4:4:4:4 format digital video tape recorder is proposed, in which the luminance signal, the difference chrominance signals R-Y and B-Y and the key signal for specical effect are recorded and reproduced in the same signal band. For example, a system for recording and reproducing the three color signals R, G, B and the key signal in the same in frequency band by a single video tape recorder is proposed.
In the digital video tape recorder which directly records on a magnetic tape video data of 4:4:4:4 type digital video processing format, it is difficult to maintain a compatibility with the prior-art digital video tape recorder of 4:2:2 format digital video signal processing and the above-mentioned problems are not yet solved.